Out of curiosity, on a rudeness/politeness scale, where would this phrase fall?
It a bit inclines toward the rudeness. If you want to show the politeness, you can add some words like "ạ", "thưa", etc. at the end or say a full sentence instead of one above like "Mọi người nhanh lên đi (ạ)!" (Everyone, please hurry up!).
people in the south of Vietnam never use that style with "ạ" :) but it doesn't mean we are rude
Yes, I know. I haven't meant that not using "ạ" is rude. "...you can add some words like "ạ", "thưa", etc.". People in the South of Vietnam hardly ever use "ạ" but they have other words to replace it.